Like others, since late Tuesday night, my phone has been blaring with text messages asking how this could have happened (as some of my friends, colleagues, and acquaintances know, I had been fully convinced that Donald Trump would win this election handily). Instead of responding in detail to every message, I will offer my explanation here.

For 2,300 years, at least since Plato’s Republic, philosophers have known how demagogues and aspiring tyrants win democratic elections. The process is straightforward, and we have now just watched it play out.

In a democracy, anyone is free to...